Diamond schottky diodes and gas sensors fabricated therefrom

Abstract

Schottky diodes and gas sensors include a diamond layer having a Schottky contact thereon and an ohmic contact thereon, wherein the diamond layer includes a highly doped region adjacent the ohmic contact to provide a low resistance ohmic contact. Dramatically reduced frequency dependence of the capacitance/voltage characteristic of Schottky diodes and gas sensors formed thereby, compared to Schottky diodes and gas sensors which do not include the highly doped region adjacent the ohmic contact, is provided. The highly doped region is preferably boron doped at a concentration of at least 10 20 atoms per cubic centimeter to form an ohmic contact with a contact resistance of less than 10 -3 Ω-cm 2 . The ohmic contact is preferably a back contact on the face of the diamond layer opposite the Schottky contact.

We claim: 
     
       1. A gas sensor comprising: a diamond layer having first and second opposing faces;   a first contact on said first face, wherein said first contact forms a Schottky barrier of predetermined Schottky barrier height between said first contact and said first face, and wherein said first contact allows gas to interact with said first face and alter said predetermined Schottky barrier height; and   a second contact on said second face, wherein said diamond layer includes a highly doped region adjacent said second contact, said highly doped region being doped at a concentration of at least 10 20  atoms per cubic centimeter, and wherein said second contact forms an ohmic contact with said highly doped region.   
     
     
       2. The gas sensor of claim 1 wherein said highly doped region comprises a region which is doped with boron at a concentration of at least 10 20  atoms per cubic centimeter. 
     
     
       3. The gas sensor of claim 1 wherein said second contact has contact resistance of less than 10 -3  Ω-cm 2 . 
     
     
       4. The gas sensor of claim 1 wherein said diamond layer is a monocrystalline diamond layer. 
     
     
       5. The gas sensor of claim 1 wherein said diamond layer is a polycrystalline diamond layer, said gas sensor further comprising at least one of a layer of undoped diamond and a thin layer of silicon dioxide, between said second contact and said polycrystalline diamond layer. 
     
     
       6. The gas sensor of claim 1 wherein said first contact comprises a catalytic metal layer which is sufficiently thin to allow gas interaction with said first face. 
     
     
       7. The gas sensor of claim 6 wherein said first contact comprises at least one of a platinum and palladium layer less than about 1000 Ångstroms thick. 
     
     
       8. The gas sensor of claim 1 further comprising at least one of a diamond substrate and a nondiamond substrate on said second face. 
     
     
       9. A gas sensor comprising: a diamond layer having first and second opposing faces;   a first contact on said first face, wherein said first contact forms a Schottky barrier of predetermined Schottky barrier height between said first contact and said first face, and wherein said first contact allows gas to interact with said first face and alter said predetermined Schottky barrier height; and   a second contact on said second face, wherein said diamond layer includes a doped region adjacent said second contact, and wherein said second contact forms an ohmic contact with said doped region; and   at least one of a diamond substrate and a nondiamond substrate on said second face, wherein said substrate includes an aperture therein, and wherein said second contact layer is formed on said second face, within said aperture.   
     
     
       10. A gas sensor comprising: a diamond layer having a Schottky contact and an ohmic contact thereon, and a highly doped region adjacent said ohmic contact, said highly doped region being doped at a concentration of at least 10 20  atoms per cubic centimeter, said gas sensor being configured such that gas external to said gas sensor is absorbed within said diamond layer, said diamond layer being responsive to gas absorbed therein to alter the barrier height of said Schottky contact and thereby provide a gas sensor.   
     
     
       11. The gas sensor of claim 10 wherein said highly doped region comprises a region which is doped with boron at a concentration of at least 10 20  atoms per cubic centimeter. 
     
     
       12. The gas sensor of claim 10 wherein said ohmic contact has contact resistance of less than 10 -3  Ω-cm 2 . 
     
     
       13. The gas sensor of claim 10 wherein said diamond layer is at least one of a monocrystalline diamond layer and a polycrystalline diamond layer. 
     
     
       14. The gas sensor of claim 10 wherein said diamond layer is a polycrystalline diamond layer, said gas sensor further comprising at least one of a layer of undoped diamond and a thin layer of silicon dioxide, between said ohmic contact and said polycrystalline diamond layer. 
     
     
       15. The gas sensor of claim 10 wherein said Schottky contact comprises a catalytic metal layer which is sufficiently thin to allow gas interaction with said diamond layer. 
     
     
       16. The gas sensor of claim 15 wherein said Schottky contact comprises at least one of a platinum and palladium layer less than about 1000 Ångstroms thick. 
     
     
       17. The gas sensor of claim 10 further comprising at least one of a diamond substrate and a nondiamond substrate on said diamond layer. 
     
     
       18. A gas sensor comprising: a diamond layer having a Schottky contact and an ohmic contact thereon, and a doped region adjacent said ohmic contact, said diamond layer being responsive to gas absorbed therein to alter the barrier height of said Schottky contact;   at least one of a diamond substrate and a nondiamond substrate on said diamond layer, wherein said substrate includes an aperture therein, and wherein said ohmic contact layer is formed on said diamond layer, within said aperture.   
     
     
       19. A diode comprising: a diamond layer having a Schottky contact and an ohmic contact thereon, and a highly doped region adjacent said ohmic contact said highly doped region being doped at a concentration which is greater than 10 20  atoms per cubic centimeter, to thereby provide a Schottky diode.   
     
     
       20. The diode of claim 19 wherein said highly doped region comprises a region which is doped with boron at a concentration of at least 10 20  atoms per cubic centimeter. 
     
     
       21. The diode of claim 19 wherein said ohmic contact has a contact resistance of less than 10 -3  Ω-cm 2 . 
     
     
       22. The diode of claim 19 wherein said diamond layer is a monocrystalline diamond layer. 
     
     
       23. The diode of claim 19 wherein said diamond layer is a polycrystalline diamond layer, said diode further comprising at least one of a layer of undoped diamond and a thin layer of silicon dioxide, between said ohmic contact and said polycrystalline diamond layer. 
     
     
       24. The diode of claim 19 wherein said Schottky contact comprises a metal layer more than about 2000 Ångstroms thick. 
     
     
       25. The diode of claim 19 further comprising at least one of a diamond substrate and a nondiamond substrate on said diamond layer. 
     
     
       26. A diode comprising: a diamond layer having a Schottky contact and an ohmic contact thereon, and a highly doped region adjacent said ohmic contact, to thereby provide a Schottky diode; and   at least one of a diamond substrate and a nondiamond substrate on said diamond layer wherein said substrate includes an aperture therein, and wherein said ohmic contact layer is formed on said diamond layer, within said aperture.